Research On Key Technologies Of MAC Protocols In Ad Hoc Networks

The function of MAC layer in ad hoc networks is to provide an effective mechanism to allocate limited wireless channel resources. In this dissertation, the MAC layer in ad hoc networks is studied, and several new algorithms to improve the MAC layer's performance and to enhance the multimedia transmission in ad hoc networks is proposed. All the contents in this dissertation are summarized as follows:In chapter 2, an improvement of Deficit Round Robin (DRR) algorithm– Enhance DRR has been proposed. Based on the premise that the original DRR is not destroyed, EDRR algorithm schedules the order that data packets are served, exhausts the remaining bits in DRR as many as possible, and effectively reduces the switching time among stations so that data packets can attain more opportunity to be served. Meanwhile, voice packets have higher transmission priority. As a result, EDRR algorithm reduces end to end delay of voice traffic with stringent delay bound and improves the QoS of the network.In chapter 3, an improved algorithm of S-MAC, CS-MAC, is proposed. CS-MAC algorithm resolved the large delay problem caused by sleeping mechanism introduced in S-MAC. Based on the premise that communications between nodes are not interfered and the performance of S-MAC is not deteriorated, after the transmission of reserved data packets, each station transmits all data packets arriving during the transmission to occupy the channel, rather than stop transmission immediately. Therefore, CS-MAC algorithm reduces contention access time, switching time and end-to-end delay of data packets, improves network throughput.In Chapter 4, a concurrent transmission MAC protocol, C-MAC is proposed. In wireless networks, throughput will be improved if more nodes been scheduled to concurrent send packets. To maximally utilize the concurrent transmission opportunity in wireless ad hoc networks, Base on GPS. Each node calculates an appropriate power to send packets, so this method avoids interference between nodes and improves network throughput and delay performance while increasing the concurrent transmission pairs.